Spout control system

ABSTRACT

The lateral swing of a discharge spout on a forage harvester is magnetically governed such that the spout is kept in proper coordination with the crop inlet port of a trailing wagon as the harvester is negotiated through turns. A wire loop encircling the wagon, upon excitation by an AC signal, produces a magnetic field which is sensed by a signal coil mounted on the discharge spout and adapted for common movement therewith. The signal coil has an output voltage, the amplitude of which varies as the wagon swings relative to the spout. This output voltage is compared with the loop excitation signal to denote any phase differential and the resulting voltage signal, after being passed through a dead band generator, drives a bi-directional electrohydraulic unit which swivelly swings the discharge spout into proper coordination with the crop inlet of the wagon.

United States Patent [1 1 Symonds [451 Jan. 22, 1974 SPOUT CONTROLSYSTEM [75] Inventor: Dean Homer Symonds, Davenport,

Iowa

[73] Assignee: Deere & Company, Moline, 111.

[22] Filed: Jan. 15, 1973 [21] Appl. No.: 323,984

Primary ExaminerR0bert G. Sheridan POSITION A POSITION B 57 ABSTRACT Thelateral swing of a discharge spout on a forage harvester is magneticallygoverned such that the spout is kept in proper coordination with thecrop inlet port of a trailing wagon as the harvester is negotiatedthrough turns. A wire loop encircling the wagon, upon excitation by anAC signal, produces a magnetic field which is sensed by a signal coilmounted on the discharge spout and adapted for common movementtherewith. The signal coil has an output voltage, the amplitude of whichvaries as the wagon swings relative to the spout. This output voltage iscompared with the loop excitation signal to denote any phasedifferential and the resulting voltage signal, after being passedthrough a dead band generator, drives a bi-directional electrohydraulicunit which swivelly swings the discharge spout into proper coordinationwith the crop inlet of the wagon.

PATENTEB JAN22|974 FIG.|

POSITION A sum 1 BF 4 POSITION 8 8 m w g m r FIG.|A

PATENTEBJANZZIQH SHEET 2 BF 4 .CDUEQ mm mm" mohomhwo mwaim II IIII IPOSITIONS PATENTED JAN 22 I974 SHEET U U? 4 cac' SPOUT CONTROL SYSTEMBACKGROUND OF THE INVENTION This invention relates to agriculturalharvesting equipment and more particularly to a control system formagnetically regulating the lateral movement of a discharge spout on aforage harvester.

Oftentimes it is desirable to synchronize the lateral swinging of adischarge spout on a travelable harvester such as in gathering forages.This type of harvester is either self-propelled having a trailing wagon,or constitutes the middle implement in a three-vehicular agriculturaltrain wherein a tractor pulls the harvester and a wagon trails behindthe harvester. The wagon has a crop inlet port into which a spout on theharvester discharges the harvested forage. As the harvester isnegotiated around the corners of a field, it is necessary to laterallyswing the discharge spout relative to the harvester so that the foragecontinues to be discharged into the wagon rather than being thrown ontothe ground beside the wagon. After the turn has been negotiated, and theimplements in the vehicular train return to an in-line relationship, thespout must be swung in reverse to maintain proper dischargement of theharvested forage.

A presently used method of swivelly moving the discharge spout is toprovide the harvester with a worm and worm wheel arrangement with anelongated crank arm extending the length of the harvester to within thereach of the operator seated on the tractor. In negotiating a corner ofa field, the operator turns the crank to rotate the worm in the properdirection which in turn laterally swings the spout.

A second presently used method of swivelly moving the spout is toprovide a bi-directional electrohydraulic unit to turn the spout withthe control switch for the unit located on the tractor adjacent theoperator. During cornering, the operator actuates the control switch tooperate the unit and turn the spout in one direction and, after thecorner has been negotiated, actuates the switch to operate the unit andturn the spout in the opposite direction to return the spout to theoriginal position.

A principal disadvantage of these presently used methods of moving thespout is the fact that the operator must look back and observe the spoutto assure proper positioning while the tractor is moving forward, thuspresenting an obvious safety hazard. Also, the manual manipulationrequired distracts the operator from the driving of the tractor. Inaddition, the operator may forget to turn the spout at times and,consequently, forage will be spilled on the ground.

US. Pat. No. 2,905,343, issued to I-Ieising on 22 Sept. 1959, disclosesmechanical means for automatically swinging the discharge spout inresponse to lateral movement of the wagon.

SUMMARY OF THE INVENTION It is therefore an object of this invention topresent an improved automatic spout control device for governing thelateral movement of the discharge spout on a forage harvester.

It is still a further object of this invention to present a magneticallyoperated control system for governing the lateral swinging of adischarge spout in response to lateral movement of the crop inlet porton a trailing wagon.

The magnetic control circuit for accomplishing the above stated objectsincorporates a loop of wire wrapped around a wagon which is energizedwith an alternating current to produce a magnetic field. The angularmovement of a signal coil mounted on the discharge spout relative to thewire loop causes a voltage to be induced in the coil with a magnitudeproportional to the cosine of the angle between the coil axis and themagnetic flux vector. The phase of the voltage changes with respect tothe loop current as the coil is rotated through a null position whichrepresents the in-line relationship between the spout and the wagon cropinlet port. The signal from the antenna is detected by a synchronousphase detector which produces an output voltage having a magnitudeproportional to the cosine of the angle between the coil axis and themagnetic flux vector and having an algebraic sign determined by thephase. This output voltage is amplified and operated on by a variablegain circuit to obtain an amount of dead band. Further poweramplification is used for driving an electrohydraulic unit whichpositions the discharge spout of the harvester. The system is phased tocause the signal coil to drive to the null position where the outputsignal ceases and the electrohydraulic unit is turned off.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of theinvention will become apparent upon-reading the following detaileddescription and upon reference to the drawings, in which:

FIG. 1 is a top plan view of an agricultural harvesting vehicular trainshowing the cooperation between a swivelly mounted discharge spout of aharvester and a trailing wagon in collecting the harvested crop, thepositions of the wagon relative to the harvester during cornering beingshown in dotted lines.

FIG. 1A is a cutaway view of the base of the discharge spout showing theswivelable mounting of the spout onto the harvester and also theelectrohydraulic unit used for swingingly driving the spout.

FIG. 1B shows the angle 0, the angle between the axis of the signal coiland the magnetic flux vector.

FIG. 2 is a block diagram of one embodiment of the magnetic spoutcontrol system of this invention.

FIG. 3 is a block diagram of the electrical circuit of a secondembodiment of the magnetic spout control system of this invention.

FIG. 3A shows the relative positioning of the signal and referencecoils, elements of the invention.

FIG. 4 is a graphical representation of the various voltage signalstaken at various points in the control circuit of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT While the invention will bedescribed in connection with specific embodiments, it will be understoodthat it is not intended to limit the invention to those embodiments. Onthe contrary, it is intended to cover all alternatives, modificationsand equivalents as may be included within the spirit and scope of theinvention as defined by the appended claims.

Looking now at FIG. 1, a conventional tractor 10 provides the motivatingforce for a forage harvester 12,

which discharges the harvested crop into a trailing wagon 14 having aconventional tongue 16. The harvester 12 is connected to a conventionaldrawbar of the tractor l0, and the tongue 16 of the wagon 14 isconnected to a hitch 18 on the rear of the harvester 12. A PTO unit 20of the tractor powers the cutting, auger and blower mechanisms of theharvester through a drive shaft 22.

In operation, the tractor pulls the vehicular train through the fieldalong the rows of crop to be harvested and around the corners of thefield. A harvesting attachment 24 on the harvester 12 feeds the cropinto the harvester, where it is chopped and fed to a blower 30 whichblows the ensilage upwardly and rearwardly through a discharge spout 26into the bed of the wagon through a wagon crop inlet port28. As thewagon is negotiated around a turn, it swings laterally relative to thespout normally within a range of 1 45, as indicated by the dashed linesin FlG. 1.

As can be readily appreciated by viewing FIG. 1, if the discharge spoutwere rigidly secured to the harvester rather than being laterallymovable, as the tractor pulled the harvester around a corner of thefield the harvested forage would miss the wagon and be blown onto theground, since the harvester would negotiate the corner before the wagon.In order to overcome this difficulty, the discharge spout is swivellymounted to the harvester such that the spout can be swung laterallyduring turning to keep the discharge spout in line with the crop inletport of the wagon.

FIG. 1A depicts one of several ways of swivelly connecting the dischargespout to the outlet of the blower 30. The outlet of the blower 30 endsin a circular flange member 32 extending around the perimeter of theouter wall thereof. The lower end of discharge spout 26 carries a secondflange member 34 having an outer diameter slightly larger than the outerdiameter of the flange member 32. An L-shaped lip 36 depends downwardlyfrom the flange member 34 to encircle the flange 32, thereby swivellysecuring the discharge spout 26 to theblower 30. An electrohydraulicbi-directional drive unit 38 governs the swivelling of spout 26. Theelectrohydraulic control unit is conventionally constructed and includesan electrical motor powering a hydraulic pump which operably suppliesfluid to a cylinder for reciprocating a piston 39 connected to thedischarge spout.

As previously mentioned, this invention comprises a novel electricalcontrol system using magnetic principles for initiating the commandsignals sent to the electrohydraulic drive unit 38 for governing thebidirectional lateral swinging movement of the discharge spout 26 toassure proper positioning of the spout so that forage is continuallydischarged into the inlet port of the wagon 14.

Turning now to FIG. 2 of the drawings, the specific components of oneembodiment of the magnetic control system of this invention are shownschematically. Generally, the control circuit of this invention includesan excitation signal source 42 which furnishes a high frequency ACsignal to a magnetic transmitting device 44. The transmitting device ismounted on the wagon 14 and produces a magnetic field emanating from thewagon generally in the direction of the travel of the wagon as isdenoted by the arrows 46. The magnetic field created by the magnetictransmitting device on the wagon induces a voltage in a signal coil 48carried by the discharge spout 26 of the harvester. The voltage inducedin the signal coil has a magnitude proportional to the cosine of theangle 0, the angle between the axis of the coil and the magnetic fluxvector at the coil as is shown in FIG. 1B. The voltage induced in thesignal coil is amplified by an amplifier circuit 50 and is then passedinto a phase detector 52. Within the phase detector the induced voltageis multiplied with a square wave voltage produced by a squaring circuit54. The multiplication of the voltage induced in the signal coil and thesquaring circuit electrically determines the phase of the inducedvoltage. The resulting voltage signal is then fed into an actuator 56having a variable gain circuit to produce an amount of dead band beforethe signal is power amplified by appropriate amplifiers 58 and 60 todrive the electrohydraulic drive unit 38 in the appropriate direction toproperly coordinate the spout with the inlet port of the wagon.

The excitation signal source 42 includes an electrical oscillator havingan amplifier 62 which produces an alternating current output signal ontwo leads 64 and 66. While the invention is not limited to any specificfrequency, it has been found that an opportune frequency to obtaindesired results is 8-10 kilohertz.

The electric oscillator, as well as the remaining circuitry hereinafterdiscussed, receive power from a conventional power source (not shown) inthe normal manner.

Since the feeding of power to the circuitry is well known to thoseskilled in the art, specific reference to each connection will not bemade hereinafter.

The lead 64 carries the alternating current signal to the magnetictransmitting device 44 where the signal is fed to a second amplifier 68which biases the base of two transistors 70 and 72 through diodes 74 and76. The emitters of both transistors 70 and 72 are connected to theprimary side of a transformer 78 typically having a turn ratio of 10 tol. A loop of wire 80 consisting of at least one turn encircling thesides, top and bottom of the wagon 14 is connected acrpss the secondarywinding of the transformer 78. It is to be noted that due to well-knownmagnetic principles, loop ofvwire 80, upon excitation by the 8 kilohertzalternating current generated by the excitation signal source 42,produces a magnetic field having a flux vector 46 S.

The magnetic field created by the excitation current in the wire loop 80induces a voltage, hereinafter referred to as the signal voltage, in thesignal coil 48 mounted on the spout and adapted for common movementtherewith. The signal coil 48 includes a coil of wire 81 wrapped arounda magnetic core 82. The axis of the magnetic core 82 is physicallyarranged such that the induced voltage in the coil will have a magnitudeproportional to cosine 0, where, as before mentioned, 8 is the anglebetween the axis of the core and the magnetic flux vector at the coil.Consequently, the induced voltage has zero magnitude when the dischargespout is in proper coordination with the wagon, a condition which willhereinafter be referred to as the null position. Also, the phase of theinduced voltage changes with respect to the excitational signal currentby approximately as the signal coil 48 is rotated through the nullposition.

The induced voltage in the signal coil is passed over a lead 84 throughthe conventional amplifier circuit 50 and then fed into one input of thephase detector 52 over lead 86. The phase detector 52 multiplies theamplified signal voltage with a signal representative of the excitationsignal originating from excitation signal source 42 to determine thephase of the induced voltage. As before mentioned, the phase of thesignal voltage with respect to the excitation signal depends on whichside of null position the spout is relative to the wagon. Hence, thephase can be electrically utilized to determine which direction to drivethe spout to bring it into the null position. Multiplication isinternally accomplished by means of a switching transistor 88 having itsinput coupled to the lead 86 and gated by a square wave indicative ofthe phase of the excitation signal emanating from the squaring circuit54 over a lead 90.

The squaring circuit 54 receives the original 8 kilohertz excitationcurrent signal from the excitation signal source 42 over the lead 66,and the square wave output thereof has a phase indicative of theoriginal phase of the excitation current. Internally, the squaringcircuit 54 incorporates conventional transistors 92A, 92B, 92C and 92D,and diodes 94A and 94B electrically coupled in the normal mannerfamiliar to those skilled in the art.

Referring attention again to the phase detector 52, the multipliedsignal voltage is passed from the switching transistor 88 through afiltering and amplification network 96 to obtain a linear voltage signaloutput, which is cognizant of both the magnitude and phase of the signalvoltage.

This linear output signal from the phase detector 52 is fed into theactuator 56 over a lead 98. The actuator 56 contains a variable gaincircuit of parallel amplifiers 100 and 102 feeding the transistors 104and 106 to obtain an amount of dead band. By dead band it is .meant thatthe system is insensitive to changes in induced voltage within a limitedrange. This dead band is introduced in order to create a stable systemand to prevent fluttering or oscillating of the discharge spout when theharvester and wagon are in line and are traveling through straightstretches in the field. Depending upon the direction inwhich the spoutis to be swivelly rotated, the actuator 56 will energize either poweramplifier 58 or 60 which will then control the driving of theelectrohydraulic drive unit 38 through either lead 40A or 40B toposition the spout in a normal manner. Once the spout has been driveninto proper coordination with the inlet port of the wagon, the inducedvoltage in the signal coil 48 as before mentioned goes to zero and theelectrohydraulic unit 38 is turned off.

The operation of the control system of this invention can best beunderstood by reference to the voltage wave forms taken at variouspoints in the circuit and shown graphically in FIG. 4. The graph in FIG.4 is divided into three segments which represent three positions of thewagon relative to the discharge spout. the null position represents theproper coordination of the spout with the inlet of the wagon; that iswhen the spout is properly discharging the ensilage into the wagon. Inposition A, the wagon is swung to the right of the spout, and inposition B the wagon is swung to the left of the spout. The locations ofthe various voltage detection points as shown in FIG. 2 are as follows:

Point C and C' the output of the excitational signal source 42. Point Dthe output of the signal coil 48. Point E the output of the squaringcircuit 54.

Point F the signal between switching transistor 88 and the filternetwork 96 of the phase detector.

Point G the output of the phase detector 52.

Point H and H the outputs of valve actuator 56.

Looking now at Points C and C, the excitation signal current from theexcitation signal source 42 is a sine wave of a substantially constantamplitude during the full swing of relative movement between the wagonand the discharge spout. Thus, the sine wave has a substantiallyconstant magnitude in position A, the null position and position B.

At point D as the wagon travels through position A, the induced voltagehas the same phase as the excitation signal source, but the voltageamplitude varies as the angle 0 changes. As the spout nears alignmentwith the wagon, the amplitude of the induced voltage decreases until atnull position, it becomes zero. As the wagon is swung to the rightthrough position B, voltage is again induced in signal coil 42, however,the voltage is now out of phase with the excitation signal current. Asin position A, the amplitude of the induced voltage varies as the angle0 changes.

The square wave generated at point E by the squaring circuit 54 has aconstant amplitude and phase irregardless of the relative position ofthe wagon and spout.

At point F, as the wagon is swung through position A, the multipliedvoltage output of transistor 88 is in phase with the excitation signalcurrent and has the negative chopped off. As the wagon and spout travelthrough the null position, the voltage goes to zero. When the wagonswings through position B, the positive half cycles of the voltage arechopped off and the negative half cycles form the output since theinduced voltage has shifted 180 in phase with respect to the excitationsignal.

At point G, during travel of the wagon from the outer limits of positionA to the null position, the induced voltage is a function decreasing invalue until it reaches zero at the null position. As the wagon swingsfrom the null position to the outer limits of position B, the inducedvoltage is a function having a value of zero at the null position andincreasingly becoming more negative as the angle 0 becomes less.

When the wagon moves from the null position into position A beyond thedead band generated by actuator 56, a voltage appears at point H toactuate the electrically controlled valve in the bi-directionalelectrohydraulic unit 38 to cause the unit to drive the discharge spoutinto proper coordination with the wagon. Upon the attainment of the nullposition, the voltage at point H drops to zero and remains zerothroughout travel of the wagon through position B. It is well to notehere that due to the dead band generated by the actuator 56, a voltagewill not appear at H until after the wagon has swung a sufficient numberof degrees through position A to exceed the dead band, as is noted bythe dotdashes in FIG. 4.

Turning now to point H, while the wagon travels through either positionA or the null position, no voltage appears at this terminal. Likewise,there will not be any voltage at this point as the wagon begins to movethrough position B so long as the dead band, noted by dot-dashes in FIG.4, is not exceeded. However, when the wagon has laterally moved througha sufficient angle in position B to overcome the dead band, a voltageappears at point H which actuates electrohydraulic unit 38 to cause theunit to drive the spout into proper coordination with the wagon inlet.Upon attainment of the null position, the voltage at H drops to zero andremains at zero until the dead band is again exceeded.

Looking now at FIG. 3, there is shown a second embodiment of themagnetic spout control circuitry of this invention. In this embodiment,the lead 66 of the first embodiment has been replaced by a referencecoil 108, thereby eliminating the need for a lead 66.

An excitation signal source 42A excites a magnetic transmitting device44A. The excitation signal source 42A and the transmitting device 44Aperform the same functions as the excitation signal source 42 and thetransmitting device 44 shown in the first embodiment, and reference ismade to this embodiment for an understanding of the internal electronicsthereof. The transmitting device 44A, similar to the transmitting device48 of the first embodiment, includes a loop of wire encircling thesides, top and bottom of the wagon and generates a magnetic field.

A signal coil 48A is mounted on discharge spout 26 of harvester12 forcommon movement therewith and includes a magnetic core 82A having itslongitudinal axis perpendicular to the magnetic flux vector when thewagon and the discharge spout are in the null position. Thus, thevoltage signal induced in signal coil 48A will be proportional to cosine0.

The voltage induced in signal coil 48A is fed through an'amplifier 50Ainto a phase detector 52A wherein the induced voltage is multiplied toelectronically note any phase shift between the voltage induced insignal coil 48A and a reference signal from circuit 54A.

in this embodiment the input to squaring circuit 54A, rather than beingreceived over a lead 66 from the oscillator located in the excitationsignal source, as in the first embodiment, is received from the outputof a reference coil 108 mounted on the discharge spout and having avoltage induced therein by the magnetic field emanating from thetransmitting device 44A. Reference coil 108 includes a magnetic core 110, the axis of v which is perpendicular to the axis of core 82A of thesignal coil 48 and in the null position, parallel to the magnetic fluxvector at coil 108. Hence the voltage in-v duced in reference coil 108is proportional to sine rather than cosine 0. Since mathematically sine0 does not change phase as the coils 48A and 108 pass through the nullposition, any voltage induced in the reference coil 108 will notsignificantly change phase with respect to the excitation signal.Consequently, such voltage can be used in place of the voltage receivedover lead 66 from the excitation source.

For the sake of explanation, the reference coil 108 is shownschematically in FIG. 3 as being spaced from the signal coil 48A.However, the actual physical mounting of the two coils on the dischargespout 26 as depicted in FIG. 3A shows the reference coil 108 placed at aright angle and adjacent to the midpoint of signal coil 48A.

The voltage induced in the reference coil 108 is passed through a lead112 into an amplifier 114. After amplification, the induced voltage isfed over lead 116 to squaring circuit 54A which generates a square wavefor gating a switching transistor in phase detector 52A in the samemanner as squaring circuit 54 gated transistor 88 of phase detector 52in the first embodiment.

The output of the phase detector 52A is fed into the actuator 56A whichis identical in operation to the actuator 56, and reference is herebymade to the actuator 56 for an understanding of the internal componentsand workings of the valve actuator 56A. Depending upon which directionthe spout needs to be swung to become properly coordinated with thewagon, the actuator 56A energizes one or the other of two poweramplifiers 58A or 60A, which drives the electrohydraulic drive unit 38in the same manner as previously discussed. The electrohydraulic unit 38positions the forage harvester spout in appropriate direction toproperly coordinate the spout 26 with the wagon inlet port 28.

Paralleled into the circuit between the amplifier l 14 and the squaringcircuit 54A is a current gain feedback system comprising a rectifier 118which converts the AC signal to a DC signal and passes the DC signalonto a current gain amplifier 120. The current gain amplifier has anoutput connected to amplifiers 50A and 114. The current gain feedbacksystem compensates for variations in the distance between the loop ofwire of transmitter 44A encircling wagon l4 and the signal coils 48A and108 as the discharge spout laterally swings relative to the wagon. Inother words, the current feedback system keeps the amplitude of thesignal constant due to the distance between the loop and the coils.Thus, the circuit of this invention relies solely upon variations in theangle 0 for generation of a voltage to drive the discharge spout.

The operation of the second embodiment of this invention is similar tothe first embodiment. The magnetic field generated by the loop of wirewrapped around the wagon induces a voltage in the signal coil 48A andthe reference coil 108. These induced voltages are amplified and thencompared in a phase detector to electronically discern any phasedifferential between the voltage induced in the signal coil 48A and thevoltage induced in reference coil 110. After the phase differential hasbeen electronically noted, the phase detector 52A generates a resultingvoltage signal which is filtered and passed into actuator 56A whichgenerates an output signal on one of two power amplifiers to drive anelectrohydraulic valve in the proper direction to drive the spout intoproper coordination with the outlet port of the wagon. I

Thus, as the harvester is pulled through the field and negotiates acorner, the spout moves relative to the wagon and a voltage is inducedin the reference and signal coils 48A and 110 proportional to the angle6. This voltage then is electronically operated on to actuate theelectrohydraulic unit 38 which drives the spout back into coordinationwith the wagon. When the discharge spout and the wagon are properlycoordinated, the angle 6 between the signal coil and the magnetic fluxvector is and the signal voltage induced in the signal coil goes tozero, thereby causing actuator 56 to be turned off which stops anyfurther driving movement of the discharge spout.

Thus, it is apparent that there has been provided, in accordance withthe invention, a magnetic control circuit for controlling the lateralmovement of a discharge spout on a forage harvester that fully satisfiesthe objects, aims, and advantages set forth above.

While the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art in light ofthe foregoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications and variations as fall within thespirit and broad scope of the appended claims.

I claim:

I. A control circuit for actuating the drive unit for swinging thedischarge spout of a harvester in response to movement of a wagontrailing the harvester comprising:

a. an excitation signal source for generating an excitation signal;

b. transmitting means carried by the wagon for generating, uponenergization by the excitation signal, a magnetic field;

. a magnetically responsive signal coil carried by the harvester andadapted for common movement with the discharge spout thereof; said coilhaving induced therein by said magnetic field a signal voltage which isa function of the angle between the axis of the coil and the magneticflux vector at the coil;

of the phase of the excitation signal;

e. a phase detector for discerning the phase differential between thesignal voltage and the reference voltage; said phase detector having anoutput signal;

f. actuator means for actuating said drive unit in response to theoutput signal of the phase detector such that the spout is maintained inproper coordination with the wagon.

2. A control circuit as in claim 1 wherein said transmitting meansincludes at least one loop of wire wrapped around and carried by saidwagon.

3. A control circuit as in claim 1 wherein the axis of the signal coilis so positioned on said discharge spout means for producing a referencevoltage cognizant.

ation of the drive unit to prevent oscillatory movement of the dischargespout.

5. A control circuit as in claim 1 wherein said means for producing areference voltage cognizant of the phase of the excitation signalcomprises squaring circuitry having an input fed from the excitationsignal source by an electrical conduit and having an output which feedsthe phase detector.

6. A control unit as in claim 1 wherein said means for producing areference voltage cognizant of the phase of the excitation signalcomprises:

a. a reference coil mounted on the discharge spout and adapted forcommon movement therewith, said coil having induced therein an outputvoltage proportional to the trigometric sine of the angle between thesignal coil and said magnetic flux vector;

b. squaring circuitry having an input for receiving the output voltagefrom said reference coil and a reference voltage which is fed to saidphase detector.

7. A control circuit as in claim 6 further including an amplifierbetween the signal coil and the phase detector and a second amplifierbetween the reference coil and the squaring circuit.

8. A control circuit as in claim 7 further including a current gainfeedback system electrically coupled to said first and second amplifiersfor compensating for variations in distances between the transmittingmeans and the signal and reference coils.

9. A control circuit as in claim 8 wherein said current gain feedbacksystem comprises:

a. a rectifier having an input coupled to the output of said secondamplifier and an output;

b. a current amplifier having an input connected to the output of saidrectifier and having an output which is fed to said first and secondgain amplifiers wherein variations in the distance between thetransmitting means and the reference and signal coils are compensated.

1. A control circuit for actuating the drive unit for swinging thedischarge spout of a harvester in response to movement of a wagontrailing the harvester comprising: a. an excitation signal source forgenerating an excitation signal; b. transmitting means carried by thewagon for generating, upon energization by the excitation signal, amagnetic field; c. a magnetically responsive signal coil carried by theharvester and adapted for common movement with the discharge spoutthereof; said coil having induced therein by said magnetic field asignal voltage which is a function of the angle between the axis of thecoil and the magnetic flux vector at the coil; d. means for producing areference voltage cognizant of the phase of the excitation signal; e. aphase detector for discerning the phase differential between the signalvoltage and the reference voltage; said phase detector having an outputsignal; f. actuator means for actuating said drive unit in response tothe output signal of the phase detector such that the spout ismaintained in proper coordination with the wagon.
 2. A control circuitas in claim 1 wherein said transmitting means includes at least one loopof wire wrapped around and carried by said wagon.
 3. A control circuitas in claim 1 wherein the axis of the signal coil is so positioned onsaid discharge spout that the signal voltage induced therein by themagnetic field is a function of the trigometric cosine of the anglebetween the axis of the coil and said magnetic flux vector.
 4. A controlcircuit as in claim 1 wherein said actuator includes dead band circuitryfor stabilizing the actuation of the drive unit to prevent oscillatorymovement of the discharge spout.
 5. A control circuit as in claim 1wherein said means for producing a reference voltage cognizant of thephase of the excitation signal comprises squaring circuitry having aninput fed from the excitation signal source by an electrical conduit andhaving an output which feeds the phase detector.
 6. A control unit as inclaim 1 wherein said means for producing a reference voltage cognizantof the phase of the excitation signal comprises: a. a reference coilmounted on the discharge spout and adapted for common movementtherewith, said coil having induced therein an output voltageproportional to the trigometric sine of the angle between the signalcoil and said magnetic flux vector; b. squaring circuitry having aninput for receiving the output voltage from said reference coil and areference voltage which is fed to said phase detector.
 7. A controlcircuit as in claim 6 further including an amplifier between the signalcoil and the phase detector and a second amplifier between the referencecoil and the squaring circuit.
 8. A control circuit as in claim 7further including a current gain feedback system electrically coupled tosaid first and second amplifiers for compensating for variations indistances between the transmitting means and the signal and referencecoils.
 9. A control circuit as in claim 8 wherein said current gainfeedback system comprises: a. a rectifier having an input coupled to theoutput of said second amplifier and an output; b. a current amplifierhaving an input connected to the output of said rectifier and having anoutput which is fed to said first and second gain amplifiers whereinvariations in the distance between the transmitting means and thereference and signal coils are compensated.